chapter 4: routing dynamic · process of configuring and maintaining static routes disadvantages of...

CHAPTER 4: ROUTING DYNAMIC

Routing & Switching

CHAPTER4

4.1 Dynamic Routing Protocols

4.2 Distance Vector Dynamic Routing

4.3 RIP and RIPng Routing

4.4 Link-State Dynamic Routing

4.5 The Routing Table

4.6 Summary

ROUTING ?

TYPES OF ROUTING PROTOCOLS

CLASSIFYING ROUTING PROTOCOLS

DYNAMIC ROUTING PROTOCOL OPERATION

THE EVOLUTION OF DYNAMIC ROUTING PROTOCOLS

• Dynamic routing protocols used in networks since the late 1980s

• Newer versions support the communication based on IPv6

Routing Protocols Classification

Purpose of Dynamic Routing Protocols ?


PURPOSE OF DYNAMIC ROUTING PROTOCOLS

Routing Protocols are used to facilitate the exchange of routing information between routers.

The purpose of dynamic routing protocols includes:

• Discovery of remote networks

• Maintaining up-to-date routing information

• Choosing the best path to destination networks

• Ability to find a new best path if the current path is no longer available


PURPOSE OF DYNAMIC ROUTING PROTOCOLS (CONT.)

Main components of dynamic routing protocols include:

• Data structures - Routing protocols typically use tables or databases for its operations. This information is kept in RAM.

• Routing protocol messages - Routing protocols use various types of messages to discover neighboring routers, exchange routing information, and other tasks to learn and maintain accurate information about the network.

• Algorithm - Routing protocols use algorithms for facilitating routing information for best path determination.


PURPOSE OF DYNAMIC ROUTING PROTOCOLS (CONT.)

Advantages and Disadvantages

of dynamic routing ?


THE ROLE OF DYNAMIC ROUTING PROTOCOLS

Advantages of dynamic routing include: Automatically share information about remote networks Determine the best path to each network and add this information

to their routing tables Compared to static routing, dynamic routing protocols require less

administrative overhead Help the network administrator manage the time-consuming

process of configuring and maintaining static routes

Disadvantages of dynamic routing include: Part of a router’s resources are dedicated for protocol operation,

including CPU time and network link bandwidth Times when static routing is more appropriate

Dynamic verses Static Routing

DYNAMIC VERSES STATIC ROUTING

USING STATIC ROUTING

Networks typically use a combination of both static and dynamic routing.

Static routing has several primary uses:

• Providing ease of routing table maintenance in smaller networks that are not expected to grow significantly.

• Routing to and from a stub network. A network with only one default route out and no knowledge of any remote networks.

• Accessing a single default router. This is used to represent a path to any network that does not have a match in the routing table.


USING STATIC ROUTING (CONT.)


STATIC ROUTING SCORECARD


DYNAMIC ROUTING SCORECARD

ROUTING PROTOCOL OPERATING FUNDAMENTALS

ACHIEVING CONVERGENCE

The network is converged when all routers have complete and accurate information about the entire network:

Convergence time is the time it takes routers to share information,

calculate best paths, and update their routing tables.

A network is not completely operable until the network has converged.

Convergence properties include the speed of propagation of routing

information and the calculation of optimal paths. The speed of propagation refers to the amount of time it takes for routers within the network to forward routing information.

Generally, older protocols, such as RIP, are slow to converge, whereas modern protocols, such as EIGRP and OSPF, converge more quickly.


IGP AND EGP ROUTING PROTOCOLS

Interior Gateway Protocols (IGP) - Used for routing

within an AS Include RIP, EIGRP,

OSPF, and IS-IS Exterior Gateway Protocols (EGP) - Used for routing

between AS Official routing

protocol used by the Internet


DISTANCE VECTOR ROUTING PROTOCOLS

Distance vector IPv4 IGPs: RIPv1 - First generation

legacy protocol RIPv2 - Simple distance

vector routing protocol IGRP - First generation

Cisco proprietary protocol (obsolete)

EIGRP - Advanced version of distance vector routing

For R1, 172.16.3.0/24 is one hop away (distance). It can be reached

through R2 (vector).


DISTANCE VECTOR OR LINK-STATE ROUTING PROTOCOLS

Distance vector protocols use routers as sign posts along the

path to the final destination.

A link-state routing protocol is like having a complete map of the network topology. The sign posts along the way from source to destination are not necessary, because all link-state routers are using an identical map of the network. A link-state router uses the link-state information to create a topology map and to select the best path to all destination networks in the topology.


LINK-STATE ROUTING PROTOCOLS

Link-state IPv4 IGPs: OSPF - Popular

standards based routing protocol

IS-IS - Popular in provider networks.


CLASSFUL ROUTING PROTOCOLS

Classful routing protocols do not send subnet mask information in their routing updates: Only RIPv1 and IGRP are classful. Created when network addresses were allocated based

on classes (class A, B, or C). Cannot provide variable length subnet masks (VLSMs)

and classless interdomain routing (CIDR). Create problems in discontiguous networks.


CLASSLESS ROUTING PROTOCOLS

Classless routing protocols include subnet mask information in the routing updates: RIPv2, EIGRP, OSPF, and IS_IS Support VLSM and CIDR IPv6 routing protocols


ROUTING PROTOCOL CHARACTERISTICS


ROUTING PROTOCOL METRICS

A metric is a measurable value that is assigned by the routing protocol to different routes based on the usefulness of that route: Used to determine the overall “cost” of a path from

source to destination. Routing protocols determine the best path based on

the route with the lowest cost.

DISTANCE VECTOR ROUTING PROTOCOL OPERATION

DISTANCE VECTOR TECHNOLOGIES

Distance vector routing protocols: Share updates between neighbors Not aware of the network topology Some send periodic updates to

broadcast IP 255.255.255.255 even if topology has not changed

Updates consume bandwidth and network device CPU resources

RIPv2 and EIGRP use multicast addresses

EIGRP will only send an update when topology has changed

DISTANCE VECTOR ROUTING PROTOCOL OPERATION

DISTANCE VECTOR ALGORITHM

RIP uses the Bellman-Ford algorithm as its routing algorithm. IGRP and EIGRP use the Diffusing Update Algorithm (DUAL) routing algorithm developed by Cisco.

TYPES OF DISTANCE VECTOR ROUTING PROTOCOLS

ROUTING INFORMATION PROTOCOL

RIPng is based on RIPv2 with a 15 hop limitation and the administrative distance of 120

Updates use UDP

port 520

Routing updates

broadcasted every 30 seconds

TYPES OF DISTANCE VECTOR ROUTING PROTOCOLS

ENHANCED INTERIOR-GATEWAY ROUTING PROTOCOL

EIGRP: Is bounded

triggered updates Uses a Hello

keepalives mechanism

Maintains a topology table

Supports rapid convergence

Is a multiple network layer protocol support

CONFIGURING THE RIP PROTOCOL

ROUTER RIP CONFIGURATION MODE ADVERTISING NETWORKS

LINK-STATE ROUTING PROTOCOL OPERATION

SHORTEST PATH FIRST PROTOCOLS

LINK-STATE ROUTING PROTOCOL OPERATION

DIJKSTRA’S ALGORITHM

LINK-STATE UPDATES

LINK-STATE ROUTING PROCESS

LINK-STATE UPDATES

LINK AND LINK-STATE

The first step in the link-state routing process is that each router learns about its own links and its own directly connected networks.

LINK-STATE UPDATES

SAY HELLO

The second step in the link-state routing process is that each router is responsible for meeting its neighbors on directly connected networks.

LINK-STATE UPDATES

SAY HELLO

The third step in the link-state routing process is that each router builds a link-state packet (LSP) containing the state of each directly connected link.

1. R1; Ethernet network 10.1.0.0/16; Cost 2

2. R1 -> R2; Serial point-to-point network; 10.2.0.0/16; Cost 20



LINK-STATE UPDATES

FLOODING THE LSP

The fourth step in the link-state routing process is that each router floods the LSP to all neighbors, who then store all LSPs received in a database.

LINK-STATE UPDATES

BUILDING THE LINK-STATE DATABASE

The final step in the link-state routing process is that each router uses the database to construct a complete map of the topology and computes the best path to each destination network.

LINK-STATE UPDATES

BUILDING THE SPF TREE

LINK-STATE UPDATES

ADDING OSPF ROUTES TO THE ROUTING TABLE

WHY USE LINK-STATE ROUTING PROTOCOLS

WHY USE LINK-STATE PROTOCOLS?

CHAPTER 4: SUMMARY

Dynamic routing protocols:

• Used by routers to automatically learn about remote networks from other routers

• Purpose includes: discovery of remote networks, maintaining up-to-date routing information, choosing the best path to destination networks, and ability to find a new best path if the current path is no longer available

• Best choice for large networks but static routing is better for stub networks.

• Function to inform other routers about changes

• Can be classified as either classful or classless, distance-vector or link-state, and an interior or an exterior gateway protocol

CHAPTER 4: SUMMARY (CONT.)

Dynamic routing protocols:

• A link-state routing protocol can create a complete view or topology of the network by gathering information from all of the other routers

• Metrics are used to determine the best path or shortest path to reach a destination network

• Different routing protocols may use different (hops, bandwidth, delay, reliability, and load)

• Show ip protocols command displays the IPv4 routing protocol settings currently configured on the router, for IPv6, use show ipv6 protocols

CHAPTER : 4SUMMARY (CONT.) Dynamic routing protocols:

• Cisco routers use the administrative distance value to determine which routing source to use

• Each dynamic routing protocol has a unique administrative value, along with static routes and directly connected networks, lower is preferred the route

• Directly connected networks are preferred source, followed by static routes and then various dynamic routing protocols

• An OSPF link is an interface on a router, information about the state of the links is known as link-states

• Link-state routing protocols apply Dijkstra’s algorithm to calculate the best path route which uses accumulated costs along each path, from source to destination, to determine the total cost of a route

TERIMA KASIH

Thank you very much for your kind attention

chapter 4: routing dynamic · process of configuring and maintaining static routes disadvantages of...

Documents